Chiral expoxides or chiral 1,2-diols have been widely used to prepare pharmaceuticals and agriculture products having optical properties (U.S. Pat. No. 5,071,868; Tetrahedron Lett., Vol. 28, No. 16, 1783, 1987; J. Org. Chem., Vol. 64, 8741, 1999). Even if these chiral epoxides or chiral 1,2-diols having high optical purity are very useful industrially, use of these compounds has been restricted because the preparation of such compounds is too difficult to produce in a large scale with low manufacturing price.
A preparation method of chiral epichlohydrins as one of chiral expoxides is disclosed using microorganism in EP 431,970 and JP 90-257895 and 94-211822. However, it is not recommended because the productivity is low and it requires two-step process. Another preparation method of chiral epichlohydrins from chiral sulfonyloxyhaloalcohol derivatives obtained from mannitol derivatives is disclosed in U.S. Pat. No. 4,408,063; and J. Org. chem., Vol 43, 4876, 1978. Another preparation method of chiral epichlohydrins from 3-chloro-1,2-propanediol is also disclosed in Syn. Lett No. 12, 1927, 1999. However, these processes are required multi-step syntheses, so that they are also deficient to use for the industrial purpose.
Methods for preparing chiral expoxides generally use a chiral catalyst having stereoselectivity which hydrolyzes stereoselectively only one isomer from racemic epoxides mixed 50 and 50 of each isomer and leaves the un-hydrolyzed isomer in the reaction medium. However, the chiral catalyst used for said stereoselective hydrolysis is usually expensive. Therefore, if it cannot be re-used, it becomes difficult to use for the industrial purpose.
Stereoselective hydrolyses of chiral epoxides using chiral salen catalyst as a chiral catalyst are recently disclosed in Science, Vol. 277, 936, 1997; U.S. Pat. Nos. 5,665,890 and 5,929,232; and WO00/09463 and WO91/14694. It has been reported that the use of chiral salen catalyst provides higher yield with higher optical purity compared to uses of other chiral catalysts. However, it is reported that after hydrolysis of a racemic epoxide using conventional chiral salen catalyst, the product chiral epoxide is racemized as time goes in pages 86-87 of WO00/09463. When this hydrolysis is performed for mass production, the racemization of the product becomes deepened since it takes longer to perform the distillation to obtain the desired product, thus resulting in decrease of optical purity of the chiral epoxide. Therefore, the use of chiral salen catalyst in the production of chiral epoxides is limited for the above-mentioned reasons.
Further, when conventional chiral salen catalysts are reused, it requires an activation process after each use because activities thereof are rapidly decreased. Even if the catalyst is activated after used, the optical activity of the product prepared by using reused catalyst is remarkably lower than that of the product prepared by using fresh catalyst. Thus, there is limited to reuse. Such problems increase the manufacturing price of producing chiral epoxides.
Consequently, demand to produce chiral compounds such as chiral epoxides or chiral 1,2-diols efficiently and economically has been highly increased with the importance of such compounds to prepare pharmaceuticals and agriculture products.